﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BaseHelper.Encrypt
{
    public class CRCHelper
    {
        public static ushort CRC16(byte[] ptr, int len)
        {
            short i;
            short index = 0;
            ushort crc = 0;
            while (len-- != 0)
            {
                for (i = 0x80; i != 0; i /= 2)
                {
                    if ((crc & 0x8000) != 0)
                    {
                        crc *= 2; crc ^= 0x8005;
                    }
                    else
                        crc *= 2;

                    if ((ptr[index] & i) != 0)
                        crc ^= 0x8005;
                }
                index++;
            }
            return crc;
        }

        public static ushort CRC16_XMODEM(byte[] data,int len)
        {
            ushort poly = 0x1021;
            ushort[] table = new ushort[256];
            ushort initialValue = 0x0;
            ushort temp, a;
            ushort crc = initialValue;
            for (int i = 0; i < table.Length; ++i)
            {
                temp = 0;
                a = (ushort)(i << 8);
                for (int j = 0; j < 8; ++j)
                {
                    if (((temp ^ a) & 0x8000) != 0)
                        temp = (ushort)((temp << 1) ^ poly);
                    else
                        temp <<= 1;
                    a <<= 1;
                }
                table[i] = temp;
            }
            for (int i = 0; i < len; ++i)
            {
                crc = (ushort)((crc << 8) ^ table[((crc >> 8) ^ (0xff & data[i]))]);
            }
            byte hi = (byte)((crc & 0xFF00) >> 8);  //高位置
            byte lo = (byte)(crc & 0x00FF);         //低位置

            return crc;// new byte[] { hi, lo };
        }

        public static ushort CRC16_CCITT(byte[] data, int len)
        {
            ushort[] s_CRCValue = new ushort[] { 
                0, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, 
                0x1081, 0x108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, 
                0x2102, 0x308b, 0x210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd, 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5, 
                0x3183, 0x200a, 0x1291, 0x318, 0x77a7, 0x662e, 0x54b5, 0x453c, 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974, 
                0x4204, 0x538d, 0x6116, 0x709f, 0x420, 0x15a9, 0x2732, 0x36bb, 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, 
                0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x528, 0x37b3, 0x263a, 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, 
                0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x630, 0x17b9, 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1, 
                0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x738, 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70, 
                0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7, 0x840, 0x19c, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff, 
                0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, 0x18c1, 0x948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, 
                0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, 0x2942, 0x38cb, 0xa50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, 
                0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134, 0x39c3, 0x284a, 0x1ad1, 0xb58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c, 
                0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, 0x4a44, 0x5bcd, 0x6956, 0x78df, 0xc60, 0x1de9, 0x2f72, 0x3efb, 
                0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232, 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0xd68, 0x3ff3, 0x2e7a, 
                0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0xe70, 0x1ff9, 
                0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0xf78
               };


            ushort num = 0xffff;
            for (int i = 0; i < len; i++)
            {
                num = (ushort)((num >> 8) ^ s_CRCValue[(num ^ data[i]) & 0xff]);
            }
            return num;
        }


        public static ushort CRC16_MODBUS(byte[] bytes,int len)
        {
            ushort value;
            ushort newLoad = 0xffff, In_value;
            int count = 0;
            for (int i = 0; i < len; i++)
            {
                value = (ushort)bytes[i];
                newLoad = (ushort)(Convert.ToInt32(value) ^ Convert.ToInt32(newLoad));
                In_value = 0xA001;
                while (count < 8)
                {
                    if (Convert.ToInt32(newLoad) % 2 == 1)//判断最低位是否为1
                    {
                        newLoad -= 0x00001;
                        newLoad = (ushort)(Convert.ToInt32(newLoad) / 2);//右移一位
                        count++;//计数器加一
                        newLoad = (ushort)(Convert.ToInt32(newLoad) ^ Convert.ToInt32(In_value));//异或操作
                    }
                    else
                    {
                        newLoad = (ushort)(Convert.ToInt32(newLoad) / 2);//右移一位
                        count++;//计数器加一
                    }
                }
                count = 0;
            }
            return newLoad;
        }
    }
}
